Here are the rules, made up for 13 players:
-Game starts with 1 vampire who has some special 'powers', 1 priest, 3 villagers with garlic and 8 normal villagers.
-Roles:

*Vampire: The vampires infect villagers at night. A villager does NOT get to know that he was infected at night. After the next voting, the infected villager secretly turns into a vampire. Vampires do always know each other!
Vampires will also get a pm explaining to them what role the villager had that they tried to infect.

*Priest: A priest can bless villagers at night. He blesses villagers before the vampires infect. A blessed villager cannot be infected for the rest of the game. The priest cannot bless himself. If the priest blesses a vampire, nothing does happen. A villager does not know when he is blessed.
(so if the priest and the vamps chose the same target at night, the vamps have bad luck)
When vampires tries to infect the priest the priest will die immediatly.

*Garlic Villagers: (more players mean more garlicowners): They do now know in the beginning that they have these powers but it is also revealed when they die or when they are attacked at night. If a garlic villager is attacked at night, he survives this attack and half of the vampires die but the garlic villager still become infected after the attack. It's always the youngest vampires that die first.
1 vampire -> 0 die
2 vampire -> 1 dies
3 vampire -> 1 dies
4 vampire -> 2 dies
and so on
A villager loses his garlic after he was attacked and becomes infected.

*Villager: Same as usal

-Voting is the same as usual.
-If the vampires cannot infect someone at night (either because the target is blessed or because they didn't send a PM) the youngest vampire will die due to a lack of blood
-Villagers win when every vampire is dead
-Vampires win, when there is an equal amount of vills and vamps
-The original vampire can only die by voting!!!
-The vampires decide together on target they want to infect tonight like the wolves do in a normal WG.

The goal for the first vampire is to infect as many villagers as possible and to survive by turning everybody into vampires.

The goal for the villagers is to survive. As long as he is a vill he has to figure out who the original vampire is.
When a villager turns into a vampire, his chances on surving drops! He will have to work with the other vamps in order to survive.
Those who survived til the end are the winners

So, who's interested? Maybe an experimental round is held in the playground.

It's now necessary, I think, so I add the FAQ here:
Q: Will the game start at day or at night?
A: It will start at night.

Q: Will the game run in WG forum or in the Playground?
A: Wolfgame forum has some advantages (no interferences from dead or non players) so it's certainly held in WG.

Q: Can the priest be infected?
A: No, He can't when vampires tries to infect the priest the priest will die.

Q: Will the power of the first vampire be passed over to the next oldest vamp?
A: No. Once the first vampire is voted, it is possible that the villagers win the game at night: When there is only one vampire left and he cannot infect a new target (because of blessing) he will die.

Q: If the game starts at night, will the priest be able to bless the first player?
A: Yes, the game will certainly start at night and both the vampire and the priest can do an action.

Q: Will there be a PIW (priest in waiting).
A: No.

Q: Will the vampires know when they have infected the priest?
A: Yes, because the priest instantly dies.

Q: What actions and what roles will be announced?
A: The amount of vampires, garlic villagers, normal villagers and if there is a priest IS announced. Whether there is any infected villager IS NOT announced. It IS NOT announced if the priest blessed a villager and night NOR when the first vampire is voted. Each player gets to know about the other vampires when he turns into a vampire (that is after the voting). A player does not get to know when he is infected nor blessed nor was attacked carrying garlic!

Q: Can the vampires tell a target that they have infected him in the night?
A: Uhm... yes? But they might expose their roles

Q: What happens when a blessed garlic owner is attacked?
A: First, half of the vampires die of the garlic. Then 1 vampire dies of the lack of blood. The villager is not infected but he gets rid of his garlic (not so dramatic, however^^). The Mastervampire cannot die by this incident.

Q: When there is only one vamp left but there still is an infected one and the vamp gets voted, what will happen then?
A: The Villagers will win the game, (An infected vill needs the presence of a real vamp to transform(RP-explanation))

Q: When more than 1 vamps die at once, will the vills know the age of the vamps?
A: No. They are all just listed in a random or alphabetical order.

Q: Will blessing stay forever?
A: Once blessed, always blessed. A blessed villager cannot lose his blessing. Even after a vampire's attack the villager is still blessed. By the way, he doesn't know when he was attacked.